Winter 2017-18: Discussion

Lucreto

sryanbruen wrote: »

4-5c in crisp Winter sunshine is always very exciting for me.

If that is all we get this Winter I would be happy. There hasn't been many days like that over the past few years.

pauldry

In the NW we are struggling for any 24hr period dry

Even the cold weather brought 24 hrs of hailstones that kept melting

Some bad flooding Saturday morning in Sligo

More hailstones this week too it seems.

Maybe drier after that

esposito

sryanbruen wrote: »

He said the same last year for the early part of the Winter:

https://twitter.com/liamdutton/status/934821408240218112

He's probably fishing for likes and retweets! Although it is looking like a cold outlook alright.

I just hope it dosent get mild over the xmas holiday period.

arctictree

Since Friday is the 1st of December, I'm putting this in this thread. Latest GFS showing snow showers on the east coast early Friday morning:

sryanbruen

This is the mean AO index for every notably cold Winter month, including March 2013 (at least -1.5c below the IMT average, does not have to record snow) since 1963 in reply to you BLIZZARD7 in the FI charts thread.

March 2013: -3.185
January 2011: -1.683 (this month's IMT was -1.4c below the average though)
December 2010: -2.631
February 2010: -4.266
January 2010: -2.587
December 2009: -3.413

2009/10 had the most negative AO on record overall.

December 1995: -2.127
February 1991: -0.876 (only included this out of people's interest, its IMT was -0.8c below the average)
January 1987: -1.148 (another one included out of people's interest, its IMT was also -0.8c below the average)
February 1986: -2.904
January 1985: -2.806
January 1982: -0.883 (yet again another one included out of people's interest, its IMT was only -0.3c below the average despite the extreme cold and snow)
December 1981: -1.216
February 1979: -0.697
January 1979: -2.233
January 1977: -3.767
December 1976: -2.074
February 1969: -3.114
February 1968: -2.154

I have not calculated the IMTs before 1968 with the exception of 1963.

February 1963: -1.721
January 1963: -3.311

And to no surprise, all the figures are negative. Many of them are very negative. I'll remind you, these are MONTHLY means. Coincidence? I think not.

AO info is from NOAA.

MJohnston

sryanbruen - what about November 2010 when the first big snowfall happened?

sryanbruen

MJohnston wrote: »

sryanbruen - what about November 2010 when the first big snowfall happened?

The AO for November 2010 was only -0.376 but that's all down to the monthly variations it had.

Here's the AO chart including November's daily AO indexes with November and November 26th marked for you.

JCX BXC

The Met Office outlook is good (According to ME it's not possible to forecast this far out, strange their UK counterpart disagrees )

It is expected to be rather cloudy for most on Saturday, with outbreaks of rain or drizzle at times. Breezy too, especially around the coasts. Feeling milder than earlier in the week, with temperatures nearer to average for the beginning of December. A north to south split is favoured from Sunday and into early next week. Turning colder once again across the north of the UK, with frosty weather returning, along with sunshine and showers, some wintry. However, it may stay slightly less cold in the south with the risk of some rain here at times. Thereafter, a cold northerly airstream may become established across all areas, with widespread night frost and sunshine and showers by day, the showers wintry even to low levels.

Oneiric 3

JCX BXC wrote: »

The Met Office outlook is good (According to ME it's not possible to forecast this far out, strange their UK counterpart disagrees )

The UK Met office extended outlooks are based entirely on what the EC15/30 shows at the time of their forecast, which is more based on trends than actual specifics. I think it is a case that they just are more willing to stick their necks out on a medium range forecast such as the one you posted than Met Éireann is.

sryanbruen

One or two GFS ensembles are nearly going off the chart for the AO.

BLIZZARD7

sryanbruen wrote: »

One or two GFS ensembles are nearly going off the chart for the AO.

Always a good sign when looking for a prolonged cold spell... We have a long way to go yet though.

sryanbruen

BLIZZARD7 wrote: »

Always a good sign when looking for a prolonged cold spell... We have a long way to go yet though.

The ECM 12z is an absolute mess by the way .

sryanbruen

The GFS 18z is also awful so is not worth my time :P. Good ol' Pub Run!

George Sunsnow

sryanbruen wrote: »

The GFS 18z is also awful so is not worth my time :P. Good ol' Pub Run!

What is a transition year student doing down the pub?
Oh I forgot it’s transition year

Regarding the last 12 hours,all may not yet be what it seems,better to take 3

sryanbruen

George Sunsnow wrote: »

What is a transition year student doing down the pub?
Oh I forgot it’s transition year

Regarding the last 12 hours,all may not yet be what it seems,better to take 3

Lol 5th year you mean :P.

And yeah Transition Year was awful haha.

I'm continuing to be optimistic and sensible. A few model runs are not the end of the world.

sryanbruen

Here is my final Winter 2017/18 forecast or thoughts.

To start it off, I would like to say that this has been the second most difficult Winter forecast to put together. The worst being last year 2016/17 thanks to a very unique QBO situation. This year, we have a unique ENSO as well as a unique November pattern. So not feeling confident at all on what I will say here at all. These were my initial early Winter thoughts:

December - Cold, dull and fairly dry.
January - Very mild, wet and stormy. Rather sunny.
February - Very wet and mild but sunny.

I said I was not expecting a cold Winter at all then despite all the reanalysis' pointing towards a blocked Winter. That was due to solar activity - not being at the most favourable phase of the solar cycle, my pessimism and not to mention that mild is more likely if you ask me. I have changed since then by looking carefully at all the methodology and bringing it all together.

Firstly, let's talk about ENSO. ENSO this year as I already briefly stated is unique. It has got going so late in the year and back in the Spring as well as early Summer in June, it looked like we were heading into an El Nino. However, a complete flip of the Pacific SST anomalies occurred during July. From that point on, it looked like we were heading into a La Nina. Up to September, it seemed that there were high chances of a moderate La Nina taking place. Historically, there have been only 4 such ENSO events since 1946/47 and there's an even split between mild and cold - two of them had mild Winters, two of them had cold Winters. One week, the SST anomalies warmed up for a bit and this caused the models to play catch up and significantly bring down the chances of a moderate La Nina. Instead, the signs were pointing towards a weak La Nina but not nearly as weak as 2016/17. Recently, the SST anomalies have become colder again leading to higher chances of a moderate La Nina. The latest figure for ENSO was -0.8 for the past week and personally, I don't see a moderate La Nina taking place at the time of making this forecast. I see a weak La Nina though. A reanalysis I posted before was of years with weak La Nina Winters preceded by weak La Nina Winters (like 2017/18 here - 2016/17 had a weak La Nina) which showed a strong sign for a Siberian block as well as a Scandinavian block but a positive AO leaving us in a battleground situation. Whilst there seemed to be good correlation between individual Winters (season as a whole) in this reanalysis, there was far too many odd ones out to consider a month by month summary going by ENSO. The strong Siberian High in the reanalysis is evident of the situation right now as we do indeed have a strong Siberian High in the mix.

Now onto solar activity. Solar activity is officially designated as very low levels but we're not in solar minimum yet. The favourable part for cold Winters going by the solar cycle is just after solar minimum. This is the one of the few things I've been very picky about for the coming Winter as a result. We're at the same stage of the solar cycle as Winter 2006/07 which was a very unsettled, zonal and mild Winter. Seeing as how eerily similar 2016/17 was to 2005/06, I thought 2006/07 and 2017/18 would have some strange similarities. So far, not at all besides solar activity. I threw this idea out the window as a result and just looked at the idea of low solar activity. I think that the fact solar activity is low opens up more opportunities for cold this Winter. I would like to also add though that Winter 1962/63 was around the same part of the solar cycle as 2017/18, which of course was the famously (or infamous :P) cold Winter. I am not seeing a 1962/63 at all however. The most extreme cold I would expect is -10c as a minimum and anomalies of -0.5 to -0.8c below average. 1962/63's IMT in comparison was around -3 to -4c below average, a huge difference. 2007/08 was around the same stage of the solar cycle as 2017/18 also. This was a mild and wet Winter, though February had some nice frosts and a notable dry spell mid-month - December had one too, so was far from the worst Winter despite a terrible January then. I wouldn't complain much with a Winter like 2007/08. Due to this solar cycle being the weakest since Solar Cycle 16, I looked at where we were right now in previous weak solar cycles to see if there's any correlation of cold Winters. There seemed to be a strong signal for cold going by this. Although this was the same with previous years and look at what happened here with solar cycle 24, Winter 2013/14, 2015/16 and 2016/17 - which were all very mild and 2015/16 being one of the warmest on record. Solar activity is a very mixed picture.

The PDO for this season has been very up and down. Since 2014/15, it has been positive which has tended to strengthen the jet stream. This year, we have had fluctuations of it going positive and negative. Right now, it's rather positive to neutral coming from a relatively negative PDO in October. I don't know much on the PDO as I discussed before but I thought I'd include it here. Not all significantly cold Winters have a negative PDO. Some examples include Winters 1984/85 to 1986/87 and 1995/96 (1995/96 is a very important Winter for this coming season as it has a lot of similarities).

The QBO is an easterly for this season. Last year was extremely difficult to pin point due to a completely unique QBO but this year in comparison, we have a very straightforward easterly QBO. This is the first easterly QBO since 2014/15. Whilst the QBO has no "direct effects" if you get me, it is clear that there is some correlation between cold Winters and easterly QBOs historically. All the following Winters have an easterly QBO as examples: 2012/13, 2009/10, 2000/01, 1995/96, 1986/87, 1984/85, 1983/84, 1981/82, 1976/77, 1968/69, 1967/68, 1962/63 and 1946/47. Every one of these Winters had significant cold at one stage at least. Just know that there are mild easterly QBO Winters too such as 2011/12 (we were very close to a cold spell in February 2012 and the first half of December 2011 was rather cool) and 2007/08 as recent examples.

I briefly stated the strong Siberian High which I feared in October would bring us a Winter similar to 2013/14. 2013 was the last year with a similar Siberian High and snow cover progression through October to 2017. However, the jet stream has traveled much further northwards in the US compared to many of the recent years leaving a large ridge of high pressure to build across the mainland US. So the cold from the Arctic is not descending into the eastern seaboard this time, as it was in 2013/14 most notably as I showed before. Winter 2013/14 was when solar maximum of Solar Cycle 24 took place also and solar activity is much lower now than it was then. We have had more northerlies during November than we have had throughout any Winter since like 2012/13 so I think we're off to a good start with that. At least we're getting some type of cold for a change whilst the eastern seaboard of the US get the mild weather.

The NAO for May 2017 was negative but we did not achieve a tri-pole. The North Atlantic band was more like cold-cold-warm, if the very North Atlantic was warm we would have a tri-pole. Due to this, a neutral NAO for Winter 2017/18 seemed likely. Since 1946/47, there has been only one Winter with a neutral NAO and that Winter was 1979/80. This was a rather close to average Winter in terms of temperatures, rainfall and sunshine. It was quite boring with little to no variation or extreme. Right now, the NAO for the Winter (or specifically December as we can't go on further) looks rather negative which would make it the first Winter since 2012/13 with a negative NAO if it were to come off. This of course was our last colder than average Winter though 2014/15 was close to average and had some cold spells, most notably the first half of February. A negative NAO is good for cold conditions but like any methodology is no guarantee - 1997/98 had a negative NAO and look at what that disaster of a Winter turned out as (thanks to a very strong El Nino). The Atlantic has been much warmer than usual compared to recent years with the infamous cold blob pretty much vanished into space. A warmer Atlantic is less conducive to storms. Not to mention, the Atlantic right now seems to be very blocked and definitely no sign of zonality taking place in the next few weeks - unless you believe some of the ridiculous and far out there model runs that haven't a clue what they're talking about.

The AO looks to be very negative into December and as I showed, many of the very cold months tend to have a very negative AO index. March 2013 was the last time we had a significantly negative AO so we're overdue one. All the negative AO means by the way is that there is northern blocking over the Arctic allowing the cold to descend into the mid-latitudes. The atmosphere has been acting up this year and the Polar Jet is further northwards over North America than usual disallowing cold to descend into the eastern seaboard of the US as I already said and power up the jet stream.

The stratosphere throughout November has shown no signs of warming up besides the second week of December on a few runs of the GFS for the past week. Historically, a SSW event is favourable in November and January if you want a cold Winter. 2010 didn't have any SSW event and the stratosphere was quite cold throughout December then. SSW is one of the more recent methodology though as it was only found out in late 2012 or early 2013 so still requires a lot of research. Going by previous occurrences, the stratosphere seems to be good for cold weather right now which you would not expect given the theory of SSW. It's strange how SSW events in each month can play out very differently for the conditions of the Winter. As we go on further into the Winter, I am expecting some sort of a stratospheric warming. The last time we had a SSW event was March 2016 - which led to a cold spell in April. And before that, January 2013 - which led to a cold spell in January as well as that cold March. I'm predicting one because I feel that we are overdue a Winter SSW event now - January 2017 was a failed SSW.

Warm Junes (like 2017) tend to be followed by cold Decembers like 2014 (for some parts of the country), 2010 and 2009. Now I don't think this is a good indicator at all in my opinion, there are far too many odd ones out. For example, December 2007, December 2006, December 2005, December 2004 - we don't have to go long back to find a consecutive run of mild Decembers that were preceded by warm Junes. December 2016 is the most recent example of course as June 2016 was also warm.

Unsettled Septembers (like 2017) tend to be followed by cold Winters. In fact, I was very surprised with how many cold Winters followed unsettled Septembers. Look at previous unsettled Septembers for example, there was 1946, 1962, 1976, 1981, 1983, 1984, 1985, 1990 for some, 1995 for east of the UK, 2000, 2008, 2010 and 2012. All of these were followed by cold Winters!

This November has been very unique as I said at the start but one notable thing the month has had is northern blocking. Many cold Winters tend to start with northern blocking in November and if you look through much of the cold Winters I have mentioned in this post, you will find that they will have northern blocking in November.

The Norwegian Sea has been very warm through the Autumn season and it's very extraordinary how warm it has been. However, it has cooled down somewhat during November and is comparable to where it was in 2016. 2016 is the closest match and there is not much comparison with other years. As a result, it's very hard to tell what this could mean for our Winter. I remember reading though that a Danish meteorology service said that this promotes blocking up there. I don't know whether to believe them but northern blocking certainly has taken place during November for a start - and for much of Autumn at that, even during the very mild October.

The models seem to not be favourable at all of a cold Winter ahead. The vast majority of them are showing a mild Winter including the infamous CFSv2 which seems to be very biased to be honest.

As somebody once said to me, it's a battle of the analogues vs the models this Winter. Who am I to believe? They're both pointing toward very different outlooks.

Well, after giving a long thought, I am going for a mixed Winter. I feel that December will be a rather cool month. My 500mb height anomaly for December showed the chance of easterlies going by the distribution of the above average heights BUT it's not as simple as that. I don't think there will be easterlies. I think it will be a mix of northerlies and temporary westerlies. The block up to the north is too strong for the westerlies to make much progress leaving them as temporary. Not to mention, the very weak Polar Vortex. Going for a rather cool, dry December. If there won't be a lot of anticyclonic gloom with the high pressure directly over us under a lack of wind then I'll go for a sunny December too. Not seeing much snow either, if any.

As for January, MT was right with saying January holds the best prospects for cold. I now see what he was referring to. My 500mb height anomaly shows us in a cold and rather unsettled pattern. I'm going for quite a cold January, the coldest since 2011. With low pressure close to us though, it will be unsettled. If the air is cold enough, there could be a lot of snow. And yes, I said a lot of snow but I also said "if" and "could" so hold your horses!

There is absolutely no sign pointing towards what February will be like. I'm going for a mild February but with a lot of variation from cold to mild. The variation will open up opportunities for snow. Like with Winter 2016/17, I think this is going to be the most unsettled month of the season. I think it will be a much sunnier February than 2017. However, it's a long way off.

In summary,

December - Rather cool, dry and sunny. Not a lot of snow.
January - Cold, wet and potentially snowy.
February - Mild but with a lot of variation. Unsettled and sunny.

My confidence on this forecast is less than 10%! It's that low.

kingshankly

When I read your winter forecast I shamefully look back to when I was 16/17
Fair flucks to ya lad

Wine Goddess

Well done Sryanbruen! Great evidence backed thinking, as well as clear discussion of the potential variables and their effects.....nobody really knows, and your opinion is at least an informed one.

George Sunsnow

There are currently no soccer punch signals for cold enough or disturbed enough wintry weather on the models for Ireland

MJohnston

Soccer punch?

sideswipe

MJohnston wrote: »

Soccer punch?

Shadow_27

Red sky in the morning - shepherds warning, blue sky at night - day.

Oneiric 3

Wine Goddess wrote: »

Well done Sryanbruen! Great evidence backed thinking, as well as clear discussion of the potential variables and their effects.....nobody really knows, and your opinion is at least an informed one.

Keep in mind that Syran is about 10 years of age or something (OK, I embellish just a little) but I think we have a real 'little M.T' in the making here.

pistolpetes11

George Sunsnow wrote: »

There are currently no soccer punch signals for cold enough or disturbed enough wintry weather on the models for Ireland

The models are swinging from run to run , I think there is a few more interesting days model watching ahead yet

Reckless Abandonment

Oneiric 3 wrote: »

Keep in mind that Syran is about 10 years of age or something (OK, I embellish just a little) but I think we have a real 'little M.T' in the making here.

With MT constantly moving house or changing internet provider we need him more and more

Oneiric 3

Reckless Abandonment wrote: »

With MT constantly moving house or changing internet provider we need him more and more

M.T will be around for a long time yet. :cool:

George Sunsnow

pistolpetes11 wrote: »

The models are swinging from run to run , I think there is a few more interesting days model watching ahead yet

1 day a week is enough for me at the moment
I’ll look again on Sunday to see where our high is
Sliding over us and into Europe I hope not but it’s a strong probability

Slow drop in temp here now 3.2/-1

Snowbiee21

Possibly a few light snow showers over Munster and inland parts of Leinster . A few streamers could pop up overnight too

George Sunsnow

Snowbiee21 wrote: »

Possibly a few light snow showers over Munster and inland parts of Leinster . A few streamers could pop up overnight too

Possibly tomorrow/Friday but they’ll be very mixed,height is your friend
I’m not expecting any conditions for proper low level or coastal snow for at least a forthright now and longer if weather coming out of conus creates Atlantic storms that will easily break through our high and send it packing back to the azores
Looks to me like a pattern change back to the usual is likely

Elmer Blooker

Extremely worrying! If we get stuck in a rut like this it could last a very long time like 88-89 and 97-98. If it happens I'll see yiz in March! Sorry for the negativity but as I said, worrying.